The present invention relates to a magnetic head and a magnetic recording/reproduction device, and, more specifically, to a magnetic head and a magnetic recording/reproduction device wherein Barkhausen noise is suppressed and high-density recording is enabled.
It is expected that magnetic recording/reproduction devices, such as hard disk drives (HDDs), will achieve even greater densities in the future as the recent trends towards smaller sizes and higher densities proceeds. To increase densities in magnetic recording, it is necessary to increase the recording track density by narrowing the xe2x80x9crecording track widthxe2x80x9d and also to increase the recording density in the longitudinal direction, in other words, the xe2x80x9clinear recording density.xe2x80x9d
To ensure that a sufficiently large reproduction signal output is obtained even when the recording track width has been reduced and also the magnitude of the magnetization used for recording has been reduced, the anisotropic magneto-resistance effect (AMR) is utilized to develop AMR heads, which have high reproduction sensitivity and are now in use. Giant magneto-resistance (GMR) has recently been utilized to develop even more sensitive spin-valve GMR heads for use, which has been realized to enable even higher reproduction sensitivities. Research is also progressing into magnetic heads that utilize tunnelling magneto-resistance (TMR).
The development and use of magnetic heads with such high levels of reproduction sensitivity has made it possible to reproduce recording signals even from extremely narrow recording track widths.
However, in order to increase the linear recording density, which is the density in the longitudinal direction of a recording track, it is necessary to reduce the gap of the magnetic head. In a prior-art magnetic head that uses a magneto-resistance effect element, a magneto-resistance effect element is inserted within a head gap. The thickness of the magneto-resistance effect element must be 20-30 nm, even with an AMR head or a spin-valve GMR head, and it is necessary to provide a distance of about 100 nm between the two shields, from consideration of insulation between the sensing element and the shields. This means that there is a large limitation on increases in linear recording density.
This problem can be solved by using a structure called a xe2x80x9cmagnetic yoke.xe2x80x9d
A schematic view of the structure of a yoke-type magnetic head is shown in FIG. 22. This yoke-type magnetic head has a pair of magnetic yokes 202 with a magnetic field detection sensor 204 connected therebetween. A gap 206 is provided in the close vicinity of the ends of the magnetic yokes 202. A magneto-resistance effect element can be used as the magnetic field detection sensor 204, by way of example.
In other words, the magneto-resistance effect element 204 is moved away from the gap 206 of the magnetic head to make it possible to ensure that the head gap is sufficiently narrow. The signal flux F from the recording medium is taken in by the head gap portion and is guided by the magnetic yokes 202, then is transferred to the magneto-resistance effect element 204 that is located at a rear portion of the magnetic head, so that the reproduction signal can be obtained from this magneto-resistance effect element 204.
Since this yoke-type magnetic head makes it possible to ensure that the head gap is sufficiently small, it is possible to increase the resolution of reproduction and thus respond to a high linear recording density. With respect to track density, the reproduction track width in the prior-art device is determined by the spacing of leads disposed on either the of the magneto-resistance effect element 204, to supply a sense current thereto, but with a yoke-type device it is possible to determine the track width by the film thickness of the magnetic yokes 202 and thus it is simpler to reduce the track width than in the prior-art device. This feature is another reason why the yoke-type magnetic head can be expected to enable sufficient respond to higher recording densities in the future.
With a yoke-type magnetic head, however, the magnetic domain walls within the magnetic material used for the magnetic yokes 202 move discontinuously. As a result, the transfer of magnetic flux is passed on to the magneto-resistance effect element 204 in a discontinuous manner, which therefore leads to large amounts of Barkhausen noise in the reproduction output from the magneto-resistance effect element 204. This noise is so great, it creates a large obstacle to the implementation of a magnetic head using such magnetic yokes 202.
With a magnetic head that uses the magnetic field detection sensor 204, it is necessary to supply a sense current to the magnetic field detection sensor 204. However, with a yoke-type device, the flow of this sense current tends to shunt into the magnetic yokes 202 from the magnetic field detection sensor 204, leading to a deterioration in sensitivity. If an insulating film of a material such as alumina is disposed between the magnetic yokes 202 and the magnetic field detection sensor 204 in order to prevent this, the xe2x80x9cpropagationxe2x80x9d of magnetic flux through that portion will worsen, which causes a problem in that the same sort of deterioration insensitivity occurs.
As described above, the yoke-type magnetic head of the prior art has problems in that Barkhausen noise is generated by discontinuous movement of the magnetic domain walls in the magnetic yokes 202, and sensitivity deteriorates, either due to the worsening of the xe2x80x9cpropagationxe2x80x9d of magnetic flux between the magnetic yokes 202 and the magnetic field detection sensor 204 or due to shunting of the flow of sense current.
The present invention was devised in recognition of these technical problems. In other words, an objective of this invention is to provide a magnetic head and a magnetic recording/reproduction device that uses the same, wherein the generation of Barkhausen noise is suppressed while, at the same time, there is no deterioration of sensitivity.
In other words, a magnetic head in accordance with the present invention comprises:
a magnetic yoke taking in a signal flux from a magnetic recording medium, the magnetic yoke having a first yoke member, a second yoke member and a magnetic gap, the magnetic gap being located between the first and second yoke members; and
a magneto-resistance effect element detecting the signal flux transferred from the magnetic yoke,
wherein the signal flux is transferred to the magneto-resistance effect element via a granular magnetic film.
In this case, a xe2x80x9cgranular magnetic filmxe2x80x9d is a thin film of a material that has a granular structure wherein minute magnetic metal particles are surrounded by a material having non-magnetic properties.
Another magnetic head in accordance with the present invention relates to a magnetic head comprising:
a magnetic yoke taking in a signal flux from a magnetic recording medium, the magnetic yoke having a first yoke member, a second yoke member and a magnetic gap, the magnetic gap being located between the first and second yoke members; and
a magneto-resistance effect element detecting the signal flux transferred from the magnetic yoke,
wherein the first and second yoke members have a plurality of magnetic domains, each of the magnetic domains having a main magnetization direction parallel or antiparallel to a first direction.
A preferred embodiment of the present invention is provided with magnetic yokes having a magnetic gap interposed therebetween on a medium-facing surface thereof, and a magneto-resistance effect element formed at a position that is a predetermined distance further backward than the medium-facing surface, wherein the magnetic yokes comprise a granular magnetic film or a granular magnetic film is interposed between the magnetic yokes and the magneto-resistance effect element.
The xe2x80x9cmedium-facing surfacexe2x80x9d corresponds to the xe2x80x9cair-bearing surfacexe2x80x9d if the magnetic head is of a xe2x80x9cfloating slidingxe2x80x9d type, and corresponds to the xe2x80x9cmedium-contacting surfacexe2x80x9d if the magnetic head is of a xe2x80x9ccontact slidingxe2x80x9d type.
A further aspect of this invention is provided with magnetic yokes having a magnetic gap interposed therebetween on a medium-facing surface thereof, and a magneto-resistance effect element formed at a position that is a predetermined distance further backward than the medium-facing surface, wherein the magnetic yokes are formed of a multi-layer film structure of a antiferromagnetic film and a granular magnetic film.
A still further aspect of this invention is provided with magnetic yokes having a magnetic gap interposed therebetween on a medium-facing surface thereof, and a magneto-resistance effect element formed at a position that is a predetermined distance further backward than the medium-facing surface, wherein magnetic domains within the magnetic yokes are miniaturized.
An even further aspect of this invention is provided with magnetic yokes having a magnetic gap interposed therebetween on a medium-facing surface thereof, and a magneto-resistance effect element formed at a position that is a predetermined distance further backward than the medium-facing surface, wherein the orientation of an anisotropic magnetic field of the magnetic yokes is substantially uniform.
Yet another aspect of this invention is provided with magnetic yokes having a magnetic gap interposed therebetween on a medium-facing surface thereof, and a magneto-resistance effect element formed at a position that is a predetermined distance further backward than the medium-facing surface; wherein the orientation of an anisotropic magnetic field of the magnetic yokes is in a radiating form.
Still another aspect of the present invention relates to a magnetic head comprising at least a pair of magnetic yokes disposed within substantially the same surface, with a magnetic gap formed between contact surfaces of those magnetic yokes, wherein the main magnetization direction of the magnetic yokes is inclined within the yoke surface.
In yet another aspect of the invention, the magnetic domains formed within the yokes are maze domains. The xe2x80x9cmaze domainsxe2x80x9d include magnetic domain structures such as xe2x80x9cstripe magnetic domainsxe2x80x9d and xe2x80x9cserpentine-like magnetic domains.xe2x80x9d
Alternatively, the yokes are formed of a multi-layer structure of at least a ferromagnetic film and an antiferromagnetic film.
Further alternatively, the yokes are formed of a antiferromagnetic material having ferromagnetic crystal grains and an antiferromagnetic material at crystal grain boundaries thereof.
A magnetic recording/reproduction device in accordance with this invention is provided with any one of the previously described magnetic heads, for recording or reproducing information with respect to a magnetic recording medium.
In this case, recording and reproduction of the information is implemented with the magnetic head and the magnetic recording medium in a state in which they are substantially in contact.
The present invention is implemented as described above and exhibits the effects described below.
In other words, the present invention makes it possible to induce a magnetic flux in the magnetic head efficiently, by using a granular magnetic film that has both advantageous soft magnetic properties and a high resistance, and, since the high resistance ensures that substantially no sense current flows into the magnetic yoke, there is substantially no deterioration in the sensitivity. It is also possible to suppress eddy currents, even when used in high-frequency regions, so the frequency response characteristics are also improved.
Furthermore, since the magnetic grains within the granular magnetic film are nano-sized, the dimensions of magnetic domains therein are also miniaturized to match that size, and thus there is also substantially no movement of the magnetic domain walls and this miniaturization also makes it possible to suppress the generation of Barkhausen noise. It is also possible to induce magnetic anisotropy in the structure by subjecting it to thermal processing within a magnetic field or by forming films within a magnetic field. In particular, it is possible to make the orientation of an anisotropic magnetic field substantially uniformly performing thermal processing within a rotational magnetic field or forming a granular magnetic film within a rotational magnetic field. That is to say, it would be extremely convenient if a film that is isotropic from the magnetic point of view could be created, to form a closed magnetic path. Similarly, it is also possible to subject the structure to radial magnetic anisotropy to induce radial magnetic anisotropy, in which case, the flow of magnetic flux is always excited along the axis of difficulty, increasing the linear response characteristics and also improving the frequency response characteristics.
The present invention also makes it possible to guide magnetic flux efficiently into the magneto-resistance effect element, while maintaining the insulation thereof, by inserting a granular magnetic film between the magnetic yoke and the magneto-resistance effect element. In that case, it becomes possible to use a soft magnetic metal film such as a film of NiFe or CoZrNb as the magnetic yoke.
In addition, the present invention makes it possible to suppress movement of the magnetic domain walls, and thus suppress the generation of Barkhausen noise, by forming the magnetic yoke of a multi-layer film consisting of an antiferromagnetic film and a granular magnetic film and because the magnetization of the granular magnetic film is focused within each magnetic domain by the exchange coupling thereof with the antiferromagnetic film. It is therefore possible to prevent the generation of Barkhausen noise even when magnetic isotropy is induced by thermal processing within a rotational magnetic field or film formation within a magnetic field.
If an antiferromagnetic film is superimposed on the structure, exchange couplings with the antiferromagnetic film can be used to induce radial magnetic anisotropy, even at lower temperatures and with weaker currents. In such a case, the flow of magnetic flux is always excited along the axis of difficulty, increasing the linear response characteristics and also improving the frequency response characteristics.
The present invention also induces magnetization that is orientated in a direction that is substantially perpendicular to the magnetic yoke surfaces, so that it is basically not magnetic anisotropy within the surface but isotropy. In other words, isotropic permeability is obtained thereby. As the magnetization approaches the perpendicular orientation even further, maze domains are formed. These magnetic domains are extremely small in comparison with the magnetic flux paths, so that changes in the magnetic domains are difficult to perceive as Barkhausen noise. It is also possible to prevent any variation with time in the magnetic domain state of the maze domains that are formed by the coupling of the soft magnetic film and the antiferromagnetic film of the yoke.
The present invention also makes it possible to implement a high-density, low-noise magnetic recording/reproduction device by using anyone of the above described magnetic heads, which has huge industrial advantages.